<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        let money = 100
        while (true) {
            let num = +prompt(`
                请您选择操作：
                1.存钱
                2.取钱
                3.查看余额
                4.退出
            `)
            if (num === 4) {
                break
            }
            switch (num) {
                case 1:
                    let cun = +prompt('请输入存款金额：')
                    money += cun
                    break
                case 2:
                    let qu = +prompt('请输入取款金额：')
                    money -= qu
                    break
                case 3:
                    alert(`您的账户余额为：${money}`)
                    break
            }
        }
    </script>
</body>

</html>